This fairly common parasite can cause poop problems for both dogs and cats.

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Coccidia are gastrointestinal protozoan parasites that live in or on the lining of the intestines. A small load of these parasites may not cause any obvious problems for your dog or cat at all. But if the numbers overwhelm your pet, you may see diarrhea and in more extreme cases, bloody diarrhea.

Coccidia do drain nutrients from pets and can interfere with digestion and absorption of food. While most healthy adult dogs shrug this parasite off and may have some immunity, in puppies, senior pets, and any pet with a chronic health condition, this can lead to serious problems and even contribute to death. Luckily, most cases of coccidiosis are minor and relatively easy to treat. 

How Do Animals Get Coccidiosis?

Coccidia require a "host" animal to live and reproduce in. The oocysts (think of them as eggs) are passed in the stool. These become infective while in the environment. Next, a dog swallows them accidentally from infected soil or while sniffing. The other possibility is that your pet catches and eats a temporary host such as a mouse.

Parasite protection is another good reason to do "poop patrol" in your yard and clean up feces frequently. If coccidia are left in your yard, your pets can get reinfected.

Is Coccidiosis in Dogs or Cats Contagious?

Coccidia are considered to be species specific. That means that they have certain species they can live and reproduce in. In species they aren't compatible with, the parasites are digested or just pass on through. Some types will infect more than one animal while others hold to just one. Most types of coccidia we see in our pets are species specific and don't cross over. Isospora is the genus of the most common coccidia seen in dogs. These are very species specific and won't transmit to people. There are a couple of exceptions among other coccidal species, however.

Cryptosporidia is a species of coccidia that has been found in public water sources and can infect both people and pets. Usually this is a minor illness (if it causes any symptoms at all) in people but can be serious for immunocompromised people such as anyone undergoing chemotherapy, people with HIV, and infants and elderly people with less than optimal immune systems.

Most of the time your veterinarian can identify the coccidial species infecting your pet with a microscopic evaluation.

Boston Terrier puppy sitting in grass looking up at the camera
Credit: chuckcollier / Getty

Signs and Symptoms of Coccidia in Dogs and Cats

Many pets will show no signs at all with a coccidial infection. The ones most likely to have diarrhea are puppies and dogs with a compromised immune system. Older pets may have some natural immunity. The Companion Animal Parasite Council estimates up to 30 percent of all puppies could have coccidia. 

Severe diarrhea can quickly lead to dehydration in young puppies. Some of these pets may also vomit which makes the dehydration worse. You might also notice your pet having some belly pain. Sometimes the diarrhea will not only be watery but will have small amounts of fresh blood apparent. 

Coccidiosis diagnosis is done via a fecal analysis at your veterinarian. The oocysts are seen under the microscope, helping your veterinarian distinguish between other causes of diarrhea, especially in puppies.

This is why all young pets should have a regular fecal check. You may catch a parasite like coccidia before any clinical signs are seen and save your pet from an illness. In addition, some puppies will have multiple parasite infections, such as roundworms or giardia as well as coccidia.

Coccidia Treatment in Dogs and Cats

There is currently only one medication officially approved for treating coccidia in dogs, called sulfadimethoxine. However, there are numerous other medications which are effectively used by veterinarians off label.

Depending on the exact medication used, your puppy may need to be treated for three to 21 days. Always follow the instructions carefully and complete the treatment schedule.

Along with medicating your puppy, you need to do some heavy-duty sanitizing to help kill any coccidia oocysts in the environment. Daily poop pick up is a must. 

Indoors, ammonia can kill coccidia oocysts but be sure to keep all your pets outside while doing this and provide good ventilation to avoid poisoning your pet. Steam cleaning and pressure washing help to provide good hygiene for a kennel situation with repeated infections.